Modular cabinets, what the catalog doesn't tell you

Summary: Modular cabinets are flexible inside their own grid, but the grid often stops just short of the real wall. Measure the wall, floor, ceiling, skirting, services, and delivery route before deciding whether stock modules, filler panels, or cut-to-size modular storage makes sense.

A friend in Utrecht tried to buy modular cabinets for the back wall of his home office last September. He had a tape measure, a pencil drawing on the back of an electricity bill, and a whole afternoon. Six hours later he ordered nothing. The wall was 2.64 m wide. The kits came in 60 and 80 cm widths. Doing the maths, three 80 cm units left him 24 cm short, and four 60 cm units left him 24 cm long, and adding a "filler panel" felt like buying a sandwich and being told the bread is sold separately.

He's an engineer. He didn't think modular furniture was supposed to require an algebra session.

This is the part of modular cabinets that the product photos skip. The grids are clean, the styling is calm, and the dimensions almost fit your wall. Almost. So this post is about what modular cabinets actually are, where the promise breaks, and what to do about it without writing a cheque to a carpenter.

What "modular" actually means in a catalog

In furniture marketing, "modular" usually means one thing: a small set of fixed-width carcasses you can combine. Most kits run on a 30 / 40 / 60 / 80 cm grid. Heights are usually 72 cm or 1.44 m or 2.16 m (multiples of a base unit). Depths are 35 or 40 cm for shallow runs, 55 or 60 cm for kitchen-grade.

You pick the modules, line them up, screw them together, add a top, add doors. Done.

That's it. There's nothing wrong with the system. It's how IKEA Pax, Vox, Tylko, String, Boon, and a dozen others work. The grid is the entire point.

The trouble is that walls are not on the grid. My friend's 2.64 m wall is not divisible by 60 or 80 cm. Most rooms aren't. Modular storage promises flexibility, and inside the system it delivers, but the system stops at the edges of the modules.

Where the modular promise breaks

Off the top of my head, here's where stock modular cabinets stop fitting:

• Walls that aren't a multiple of 10 cm
• Sloping ceilings (lofts, attics, anything Dutch-canal-house-shaped)
• Skirting boards that take 8 to 12 cm out of the bottom corner
• Radiators bumping out 6 to 9 cm
• Pipework boxing in the corner
• Window sills sitting awkwardly between two heights
• Door swings cutting into the cabinet zone

The catalog answer to all of this is "filler panels" or "end panels". Which works, sort of. You bridge the gap with a piece of plain MDF and pretend the seam isn't there. For some rooms this is fine. For a study where the back wall is going to be the only thing you look at for the next eight years, it's a slow irritation.

There's also a hidden cost. A 24 cm filler panel on a 2.64 m run is about 9% of the visible width doing nothing. You paid for storage and got dead space.

Stock kits versus cut-to-size, briefly

I priced this out for him as a quick exercise. The numbers below are rough, autumn 2025, in euros.

Three 80 cm IKEA Pax bodies plus a 24 cm filler, white, no doors, no shelves: about 540 euros. With doors and basic shelving: roughly 1,100. Fits the wall, looks fine, has a visible filler.

Four 60 cm bodies, same setup: about 620 / 1,200. Fits the wall plus 24 cm sticking out toward the doorway, which he didn't want.

A made-to-measure run, 18 mm birch ply, three carcasses at 88 cm wide each, no filler, with doors and adjustable shelves: somewhere in the 1,300 to 1,600 range depending on hardware. So a few hundred euros over IKEA, no dead panel, and it actually ends where the wall ends.

That's the whole pitch for sized-to-fit modular: you pay roughly 20 to 40% more, and you get the wall back.

What to measure before you buy any modular cabinet

Most of the time someone ends up returning modular furniture, it's because of something they didn't measure. Quick list, in order.

1. The wall width at top, middle, and bottom. They are almost never the same. Older buildings can vary by 1.5 to 3 cm across two metres.
2. Floor flatness. A 60 cm cabinet on a floor that drops 8 mm across its base will not sit flush against its neighbour. You'll see the seam.
3. Ceiling height in two or three spots, especially under sloping rooflines. If you're going floor-to-ceiling you need the lowest point.
4. Skirting board depth and height, in case you want the cabinets to sit flush against the wall instead of standing 18 mm proud.
5. Radiators, pipework, light switches, sockets. Photograph them with a tape measure in the shot. Future-you will thank present-you.
6. The doorway. Specifically, what's the longest straight piece of wood that can get from the front door to the room without a 30-degree pivot? In Amsterdam apartments this is sometimes about 2.1 m, no more.

That last one matters because some "modular" runs are sold as one piece, and the box can be 2.4 m long. Doesn't fit through a Dutch staircase. Ask me how I know.

When stock modular is fine, and when it isn't

Stock modular kits work well when:

• The wall is on the grid (a 1.8, 2.4, or 3.2 m wall is basically free)
• The room is square-ish, no slopes, no awkward radiators
• You don't mind a filler or two
• You want it next week and don't want to wait six weeks for cut panels

Stock starts to lose when:

• The space is non-standard width
• You're going floor-to-ceiling on a sloped or low ceiling
• You want the cabinet line to read as "built in" rather than "stood up against the wall"
• You're using the cabinets in a hallway, alcove, or corner where every centimetre is fought for

There's a third category, somewhere between IKEA-with-fillers and a six-week carpenter quote, which is what we ended up building knuslabs.com to do. You upload a photo, drop in the measurements, and the panels come back cut to fit the wall instead of fit to a 60 cm grid. Same flat-pack assembly, same coin-and-cam-lock hardware, none of the dead panel.

If your wall is one of the awkward ones, that's the workflow that solves it.

If you're planning the same kind of project, start with custom furniture design from room photos or compare it with custom TV unit concepts. For adjacent planning detail, read Modular rattan garden furniture, and the gap that nobody fills and Modular bathroom furniture is just storage that fits around plumbing.